Direct action avalanches (or storm snow avalanches)

Spring has suddenly turned back to Winter with plenty of snowfall above 1800 m or so in the Alps

With all this snow predicted over the next few days (and the resulting avalanche activity that will be occurring as a direct result of the storm) , I thought this would be a good time to talk about direct action avalanches. We often refer to this phenomena in our snow reports and talks when a snowstorm is happening, or about to happen.

Direct action avalanches (or storm snow avalanches)

Direct action avalanches are “avalanches that occur during or immediately after a storm or in immediate response to active control procedures”, as defined by the Cyberspace Avalanche Center.

The most well known form of ‘active control procedures’ is by using explosives, usually to try and release unstable snow before opening roads, ski runs and other forms of access, and/or to release several small ‘tolerable’ avalanches before the amount of snow on a slope gets too big and potentially destructive to structures below. Here’s one from a few years ago that got a little bigger than expected!

During this ‘direct action’ phase the snowpack is at its most unstable, and this is generally when we see the most spectacular avalanches occurring. Indeed, this is when many natural avalanches happen – during the snowstorm and just after.

However, for skiers, it is after this impressive time for observing avalanches that most accidents actually happen – in the ‘delayed action avalanche’ phase when everything seems to have calmed down. By far, most accidents involve accidental slab avalanches i.e. triggered by the victims, or someone in the area, after the ‘direct action avalanche’ phase*. These mostly happen on North’ish facing slopes in December, January and February (in the Northern Hemisphere).

I’m taking the opportunity to emphasize this because we systematically see, hear and receive many comments implying that the new snowfalls are what is going to make things really dangerous. Just because there’s still a lot of snow up there, doesn’t mean that the snowpack is unstable or dangerous for an extended amount of time. Evidence and statistics actually show that these types of assumptions (often inaccurate) and oversimplifications are what is really dangerous in avalanche terrain.

How dangerous are direct action(or storm snow) avalanches?

We don’t want to discount the very real danger of ‘direct action(or storm snow) avalanches’. However, while this danger may be true during and just after the snowstorm, it’s not uncommon for the avalanche danger rating to drop from 4 or 5/5 down to 1 or 2/5 in less than 24 hours, especially when the underlying snowpack under the fresh snow from the storm is stable. This will almost certainly be the case within about 24 hours of the storm we’re currently experiencing.

Inevitably, as off-piste and backcountry skiers and climbers, we return to the question of: Whether or not it’s ‘dangerous’? The answer is that it depends on you. It depends on: 1. Where you go (decision making i.e deciding if and when you enter into avalanche terrain); 2. How you go (risk management risk reduction options once you are in avalanche terrain); 3. How well prepared you are (crisis management -in a self contained companion search and rescue along with good understanding of how human factors easily lead us astray in avalanche terrain).

For an overview of the above see this accident reduction framework designed to facilitate reducing the chance of suddenly finding yourself in a ‘dangerous’ situation!

Back to the current situation. Big snowfall in the Alps, May 2020

Right now most of us would find it hard to get into a dangerous avalanche situation, even if we tried…. including those who live in the mountains! But, for those of us interested in the mountains, the next few days will be a great opportunity to check out the increased snowfalls and the resulting ‘direct action avalanches’.

We’ll be adding images as we observe avalanches and their aftermath. And for those of you living at altitude in the Alps at the moment, if you have any images of avalanches related to this late winter storm that you want to share, please send them in and we’ll post them on this blog over the next few days with a credit on your image or video. Please send them in WeTransfer in order to avoid compression, to hat@henrysavalanchetalk.com

No one’s skiing at the moment, but (in case you didn’t know) it’s been snowing heavily at higher altitudes in the Northern French Alps. This started on Thursday, carried on yesterday, and is due to intensify again later today, 2 May. Over 1 m of fresh (pretty wet, heavy) snow is expected above 2500 m in Val d’Isère by Sunday, and similar high resorts. At lower altitudes it’s raining, and flood warnings are out.

We’ll certainly see direct action avalanches happening on these high steep slopes above 2500 m or so (and below if there is enough snow i.e. if it doesn’t rain too much below 2500 m). During the snowstorms, these avalanches will be coming on slopes facing all directions. Then, when the sun comes out following the storm, it will increase temps on the East and then South facing slopes and they will be the first to see snow slides, then West to North.

These natural direct avalanches can be very impressive (potentially involving huge amounts of snow), possibly even coming down onto roads. Because of this, they cause a lot of consternation, and possibly they are the most talked-about types of avalanche. However, they are also the most predictable and for the most part, avoidable; rarely claiming human lives, as do cold dry slab slab avalanches. But just because accidents involving natural direct action avalanches are rare is not to say that it’s OK to go out and hang out under steep slopes with snow on them during and after a storm! It’s precisely because they are relatively predictable that common sense works.

Again – for those of you currently living at altitude in the Alps, if you have any images of avalanches related to this late-winter storm that you’d like to share, please send them in. We’ll post them on this blog over the next few days with a credit on your image or video. Please send them via WeTransfer in order to avoid compression, to hat@henrysavalanchetalk.com

*Assessing the transition period from the ‘direct action avalanche’ phase just after a storm to the ‘delayed action’ phase (assessing any shift in stability and risk) is a time best treated with extreme caution. This is when applying our accident reduction framework is really important. I also talk to numerous respected experts at moments like these!

Post Storm Update

Here below are images from during and just after this storm of April 30th – May 3rd 2020. Over a 1 m of snow was recorded at above 2500 m and progressively less down to around 1600 m due to the rain mixing in with the snow at various point through the storm.

The following image of natural direct action avalanche activity was taken towards the end of the storm on May 3rd of a series of direct action avalanches from approximately 2000 m – mostly point releases at approx 2400 m. While these are not all that big compared to the ones above 2500 m (much more snow at higher altitudes), the depths of snow in the deposition zones are still more than 1 m in most places:

Here are some others:

Please look after yourselves in these difficult COVID times, everyone. Getting out into nature and enjoying the outside world, even on brief walks, is good for the soul, which is why we’ll continue to post occasional articles like this.

Let’s hope things improve soon.

Safety is Freedom!